Commutator-small power motor

ABSTRACT

A small commutator motor ( 1 ), in particular a blower motor for motor vehicles, has a rotor shaft ( 2 ) rotatably mounted in at least one rotor bearing ( 12 ) in a motor housing ( 8, 9 ). A commutator ( 18 ) and an armature winding ( 21 ) electrically connected with the commutator ( 18 ) are arranged on the rotor shaft ( 2 ) so as to be fixed with respect to rotation relative to it. Further, brush guides ( 11 ) for receiving brushes ( 16 ) held in sliding contact at the commutator ( 18 ) and an end shield ( 10 ) which fixes the first rotor bearing ( 12 ) in place are provided. The end shield ( 10 ) and the brush guides ( 11 ) are formed as a one-piece structural component part which is a component part of the motor housing ( 8, 9 ) as a first motor housing part ( 8 ).

BACKGROUND OF THE INVENTION

The invention is directed to a small commutator motor.

A small commutator motor according to the generic part of claim 1 isknown from DE 42 15 504 A1. The small commutator motor described in thisreference is used in particular as a fan motor for motor vehicles andhas a rotor shaft which is rotatably mounted in a motor housing usingrotor bearings; a commutator and an armature winding electricallyconnected to this commutator are arranged on it so as to be fixed withrespect to rotation relative to it. Brushes guided in brush guides areheld in sliding contact on the commutator. The rotor bearings arerealized as ball bearings and each one is fixed to the rotor shaft by anend shield. These end shields are arranged at the end of the motorhousing and mounted on a pole ring. The pole ring serves for themagnetic connection of two permanent magnet poles of a statorsurrounding the rotor which are inserted in the pole ring. The pole ringis enclosed by a cylindrical housing body. The brush guides are realizedas separate structural component parts and mounted on one of the endshields. For pressing the brushes against the commutator, brush contactpressure springs are provided.

This known small commutator motor has the disadvantage that the endshield next to the brush guides and the brush guides are formed asseparate structural component parts, thus increasing the expense forassembly. Another disadvantage consists in the fact that the motorhousing is formed by the two end shields, the pole ring connecting thetwo end shields, and the housing body partially surrounding the poletube, and thus comprises, in all, four parts. Therefore, the expense forassembling the motor housing is also relatively high.

DE 196 06 487 A1 shows another small commutator motor in a modifiedconstruction. The small commutator motor known from this reference has ahousing receptacle into which the small commutator motor and a fan wheeldriven by the small commutator motor can be inserted. At the same time,the housing receptacle is also used for the air conduction of the intakeair flowing towards the fan wheel. In this realization, as well, thehousing of the small commutator motor used as the drive motor comprisesa pole ring, a housing body surrounding the pole ring, and end shieldsfor fixing the rotor bearings in position, each end shield beingconnected with the pole ring. The brush guides are also realized asseparate structural component parts. The expense for assembly that hasalready been described is therefore also present in this case.

SUMMARY OF THE INVENTION

The small commutator motor according to the invention has the advantageover the prior art that the expenditure on manufacturing and assembly isconsiderably reduced. Since the end shield situated next to the brushguides is formed as a one-piece structural component part along with thebrush guides and is, at the same time, a component part of the motorhousing, the result is an extremely compact construction that is easy toassemble. It is no longer necessary to mount the brush guides on the endshield on the one hand and the end shield on the pole ring on the otherhand. Rather, the functions of the brush guide, namely, to support ofthe rotor bearing and housing closure, are integrated in an individualstructural component part.

A second end shield provided for a second rotor bearing canadvantageously be formed integral with a second motor housing part. Inthis case, the first motor housing part advantageously closes the secondmotor housing part like a lid. The two motor housing parts can beproduced advantageously as plastic injection molded parts, resulting inlow production costs.

The rotor bearings are preferably locked to the associated end shieldsby ring-shaped holding springs. These holding springs are fixed to theassociated motor housing parts, preferably by riveting or by snappingthem in position behind projections provided at the respective motorhousing part.

It is advantageous for a pole ring connecting at least two poles ofpermanent magnets with each other to be pressed into the second motorhousing part, in which case spacer ribs formed integral with the secondmotor housing part can be provided between the second motor housing partand the pole ring. Advantageously, these spacer ribs can also be made ofan elastomer material; in this case, the second motor housing part canbe produced by means of a two-component injection molding process, andthe spacer ribs made of an elastomer material can be injection moldedonto the second motor housing part. The use of elastomer materials forthe spacer ribs results in a particularly low noise emission, since thestructure-bome noise emitted by the pole ring is damped extensively.

The axial fixing of the pole ring can be effected either by a stop onthe first motor housing part or by special catch hooks forming part ofthe second motor housing part.

The permanent magnet poles can be fixed advantageously inside the polering in that a spring element presses each of the permanent magnet polesagainst a stop projecting inward at the pole ring. In this manner,possible unavoidable deviations from the correct dimensions resultingfrom manufacture can be compensated for.

The pole ring is advantageously formed by at least two shells which areseparated from one another by gaps running axially relative to the rotorshaft. These shells of the pole ring are substantially more economicaland easier to produce than a solid ring. The shells can be made of stripstock using simple tools, for example. The gaps running between theshells have the advantage of suppressing armature cross field.

Advantageously, there can be provided at the second motor housing partan essentially radial flange on which components of control electronicsand/or one or more protective resistors can be mounted. In this case, itis particularly advantageous when first metal connections connected tothe brushes project radially out of the first motor housing part andsecond metal connections connected to the components of the controlelectronics and/or the protective resistors project from the flange ofthe second motor housing part axially toward the first connections, sothat the first and second connections can be connected with one another,for example, by welding, soldering and pressing. The relativelycomplicated wiring of the control electronics or of the protectiveresistors to the brushes which has been customary until now is no longernecessary.

If the small commutator motor is driving a fan wheel of a fan, it isadvantageous to attach additional blades to the fan wheel in the area ofthe components of the control electronics or protective resistors forcooling them.

For mounting the fan wheel on the rotor shaft in the motor housing, itis particularly advantageous when the second end shield located oppositeto the brush guides has an opening that is closed by a thin membrane ordiaphragm. When pressing the fan wheel onto the rotor shaft, the rotorshaft can be supported on the opposite side in that the rotor shaftrests on a suitable counter-piece with the intermediary of thediaphragm. The thin, flexible diaphragm prevents axial forces that occurwhen the fan wheel is being pressed on from being transferred to therotor bearing or the motor housing. At the same time, in contrast to anopen construction, the flexible diaphragm ensures that the second endshield and the second motor housing part is closed off, so that dirt isprevented from entering the motor housing.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiment examples of the invention are shown in the drawing insimplified manner and are explained in more detail in the subsequentdescription.

FIG. 1 shows a small commutator motor according to the invention in asectional view;

FIG. 2A shows partial section through a small commutator motor accordingto the invention in the area of a rotor bearing;

FIG. 2B shows partial section through a small commutator motor accordingto the invention in the area of a rotor bearing according to anembodiment example modified from FIG. 2A;

FIG. 3A shows a section along line III—III in FIG. 1;

FIG. 3B shows a section along line III—III in FIG. 1 of an embodimentexample modified from FIG. 3A;

FIG. 4 shows an axial section through the second motor housing part anda pole ring of a small commutator motor according to the invention;

FIG. 5A shows a section along line VA—VA in FIG. 1;

FIG. 5B shows a section along line VB—VB in FIG. 5A;

FIG. 6 shows a section along line VA—VA in FIG. 1 of an embodimentexample modified from 5A;

FIG. 7 shows a partial sectional view of a small commutator motoraccording to the invention to explain the contacting of components ofcontrol electronics or a protective resistor;

FIG. 8 shows a partial section through a small commutator motoraccording to the invention in the area of a rotor bearing; and

FIG. 9 shows a small commutator motor according to the invention in asectional view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a small commutator motor according to a first embodimentexample of the invention in a partial sectional view. In the depictedembodiment example, the small commutator motor, designated generally by1, is used as a blower motor for motor vehicles, for example, forventilating the radiator or for an air conditioning system. A rotorshaft 2 which is mounted rotatably is therefore connected to a fan wheel4 in the embodiment example. Fan blades 3 have been formed integral withthe curved, pot-shaped base body 5 of the fan wheel 4. The base body 5of the fan wheel 4 has a sleeve-like connecting element 6 which has beenpressed onto the rotor shaft 2 of the small commutator motor 1. The fanwheel 4 can be produced inexpensively as a plastic injection moldedpart.

Substantially inside a pot-shaped recess 7 in the base body 5 of the fanwheel 4 facing the small commutator motor 1, there is located a firstmotor housing part 8 which together with a second motor housing part 9forms a motor housing 8, 9. The first motor housing part 8 and thesecond motor housing part 9 are connected with one another in that inthe embodiment example the first motor housing part 8 is insertedaxially into the second motor housing part 9 so as to partially overlap,so that the first motor housing part 8 closing the second motor housingpart 9 like a lid. For securing the connection, the two motor housingparts 8 and 9 can be connected with one another by screwing, riveting,gluing, welding or another type of frictional connection. The two motorhousing parts 8 and 9 are preferably produced economically as plasticinjection molded parts.

According to the invention, the first motor housing part 8 forms, at thesame time, a first end shield 10 and brush guides 11 in a one-piececonstructional arrangement, i.e., the first end shield 10 and the brushguides 11 are formed as a one-piece structural component part which, asfirst motor housing part 8, is part of the motor housing 8, 9 at thesame time.

A first rotor bearing 12 is fixed in position by the end shield 10. Forthis purpose, the end shield 12 has a pocket-like recess 13 whichsurrounds the rotor bearing 12, formed in the embodiment example as asliding or friction bearing, axially on one side. A holding spring 15 isfastened at a step 14 in the end shield 10 in a manner to be describedin more detail and axially surrounds the side of the first rotor bearing12 remote of the end shield 10.

The brush guides 11, also formed integral with the first motor housingpart 8, are used for the radial guiding of brushes 16 which arepreferably formed as carbon brushes. The brushes 16 are radially held incontact with a commutator 18 by means of brush contact pressure springs17. The commutator 18 is fastened, via an insulator 19, to the rotorshaft 2 so as to be fixed with respect to rotation relative to it and isconnected via connection lines 20 with an armature winding 21 alsoarranged on the rotor shaft 2 so as to be fixed with respect to rotationrelative to it.

The first motor housing part 8 therefore has three functions in one: itis an end shield for the first rotor bearing 12, it forms brush guides11 for the brushes 16 and it is, at the same time, part of the motorhousing 8, 9. Uniting a number of functions in one structural componentpart results in an extremely compact construction and anassembly-friendly design. Armature stampings 22 project out of thearmature winding 21 which are distanced from permanent magnet poles 24and 25 by an armature gap 23. The circuit of magnetic flux is closedthrough an annular pole ring 26 which is preferably pressed into thesecond motor housing part 9. In order to achieve a radially symmetricarmature gap 23, the first motor housing part 8 and therefore the firstrotor bearing 12 are preferably centered on the pole ring 26 in that thefirst motor housing part 8 has a centering projection 27.

On the end of the housing 8, 9 located opposite to the first rotorbearing 12, a second rotor bearing 28 is provided which is also formedas a friction bearing in the embodiment example. For fixing the secondrotor bearing 28 in position, the second motor housing part 9 has asecond end shield 29 constructed so as to form one piece with it. Thesecond end shield 29 has a pocket-like recess 30 which surrounds half ofthe second rotor bearing 28 axially. Further, an annular holding spring31 is fastened to a step 32 in the second end shield 29 and fixes thesecond rotor bearing 28 axially.

During assembly, the pole ring 26 and the permanent magnet poles 24 and25 and rotor bearing 28 with the holding spring 31 are initiallypreassembled on the second motor housing part 9, and then the rotor,comprising the rotor shaft 2, armature winding 21, armature stampings 22and commutator 18, is inserted into the second motor housing part 9. Therotor bearing 12 with the holding spring 15 is preassembled in motorhousing part 9. Finally, the first motor housing part 8 is set on top ofit like a lid and pushed in axially in the direction of the second motorhousing part 8 until the necessary axial longitudinal play for the rotorbearings 12 and 28 has been set. In this position, the two motor housingparts 8 and 9 are connected with one another, for example, by welding,gluing, riveting or screwing, so that the two end shields 10 and 29 arefixed in position and the axial play is determined in this manner.

The second motor housing part 9 preferably has a flange 33 which extendsessentially radially and which at least partially closes the pot-shapedrecess 7 of the base body 5 of the fan wheel 4. Components 34 of controlelectronics and/or protective resistors can be mounted on the flange 33.For the purpose of cooling these components 34 of the controlelectronics or protective resistors, additional blades 35 are preferablyfitted to the fan wheel 4 in the area of these components 34 of thecontrol electronics or protective resistors so that the controlelectronics or protective resistors can be cooled better.

Details and advantageous further developments and improvements of theembodiment example of a small commutator motor according to theinvention shown in FIG. 1 are described with reference to FIGS. 2 to 8.

Different possibilities for attaching the ring-shaped holding spring 31to the second end shield 29 are shown in FIGS. 2A and 2B. FIGS. 2A and2B both show a partial sectional view in the area of the second rotorbearing 28. In the embodiment example shown in FIG. 2A, insideprojections 40 have been formed on integrally at the step 32 of the endshield 29. The ring-shaped holding spring 31 snaps in behind theseprojections 40 and is thus locked to the end shield 29. In theembodiment example shown in FIG. 2B, the ring-shaped holding spring 31is connected with the second end shield 29 are joined by a rivet 41,preferably by ultrasonic riveting. It is also possible for thering-shaped holding spring 31 to have sharp edges or claws which diginto the relatively soft plastic of the second end shield 29.

Naturally, fastening the holding spring 15 of the first rotor bearing 12to the first end shield 10 can be effected in the same manner.

FIGS. 3A and 3B show a section along the line III—III in FIG. 1, butwithout the inserted rotor. The second motor housing part 9 and the polering 26 are visible. In both embodiment examples shown in FIGS. 3A and3B, the pole ring 26 has been pressed into the second motor housing part9. In the case of the embodiment example shown in FIG. 3A, the pole ring26 has been pressed directly into the second motor housing part 9 insuch a way that the outer surface of the pole ring 26 sits flush on theinner surface of the second motor housing part 9. In the embodimentexample shown in FIG. 3B, on the other hand, spacer ribs 42 have beenformed integral with the inside of the second motor housing part 9 andare arranged so as to be distributed around the circumference. In thisway, the pole ring 26 is kept at a distance from the second motorhousing part 9. Correspondingly, the emission of noise is reduced bydecoupling structure-borne sound. It is particularly advantageous forthe spacer ribs 42 to be made of an elastomer material, for example,rubber. The spacer ribs 42 can then be injection molded onto the secondmotor housing part 9 in a two-component injection molding process. Theelastic design of the spacer ribs 42 further improves the acousticdecoupling between the pole ring 26 and the second motor housing part 9and thus further reduces noise emission.

A stop 43 shown in FIG. 1 can be used for fixing the pole ring 26axially in the motor housing 8, 9. Alternatively, in accordance with theembodiment example shown in FIG. 4, it is also possible to providespecial catch hooks 44 which are formed integral with the second motorhousing part 9 and engage behind a front face 45 facing the first motorhousing part 8. The catch hooks 44 can act at the pole ring 9distributed across the circumference.

FIG. 5A shows a section along line VA—VA in FIG. 1, but without therotor being inserted, so that the armature stampings 22 and the armaturewinding 21 cannot be seen in FIG. 5A. Shown are the second motor housingpart 9, the pole ring 26 and the two permanent magnet poles 24 and 25 ofthe small commutator motor 1, which is bipolar in the embodimentexample.

The pole ring 26 has a stop 50 on one side for holding each permanentmagnet pole 24 and 25, one side of the permanent magnet poles 24 and 25contacting these stops 50. A spring element 51 is used for spreading.The spring element 51 is shown more clearly in FIG. 5B which shows apartial section along line VB—VB in FIG. 5A. In the shown embodimentexample, the spring element 51 is formed of a flexible clip 52 that canbe spread open with a wire spring 53 inserted in the elastic clip 52. Inthis manner, the permanent magnet poles 24 and 25 are pressed radiallyagainst the pole ring 26 and fixed in position. A protrusion 54 isprovided on each side for fixing them axially.

The wire spring 53 and the elastic clip 52 can be produced directly inthe production line without any great manufacturing expense. Thequantity of individual parts required is relatively small. The clip 52can also be injection molded directly onto the second motor housing part9.

FIG. 6 also shows a section along line VA—VA in FIG. 1, butcorresponding to a modified embodiment example. In contrast to theembodiment example shown in FIG. 5A, the pole ring 26 is not formed inone piece in tubular shape but, rather, is composed of two shells 26 aand 26 b. The shells 26 a and 26 b can be manufactured at considerablylower expense, for example, by pressing them out of strip stock. Thiscan be carried out directly in the production line; prefabrication isnot necessary.

An axially extending gap 56 is preferably provided between the twoshells 26 a and 26 b in each instance. By means of these gaps 56,deviations from the correct dimensions resulting from manufacture can becompensated for on the one hand. On the other hand, these gaps 56 servefor the suppression of armature cross field.

FIG. 7 shows the flange 33 of the second motor housing part 9 and acomponent 34 of the electronic control circuit shown by way of example.The electronic control circuit is used, for example, to adjust the speedof the small commutator motor 1. In the embodiment example shown in FIG.7, the components 34 of the electronic control circuit, for example,resistors or capacitors, are connected with the flange 33 by means ofsnap-in locking elements 60.

First metal connections 61 project radially out of the brush guides 11of the first motor housing part 8 and are connected with the associatedbrush 16 by a movable cord. Second metal connections 62 project awayfrom the flange 33 axially relative to the rotor shaft 2 toward thefirst connections 61. The first connections 61 of the brush guides 11can be electrically connected to the second connections 62 of theelectronic control circuit in a simple manner, for example, bysoldering, welding or pressing. Complicated wiring is not necessary.

FIG. 8 shows the second end shield 29 at the second motor housing part 9and the second rotor bearing 28. An opening 63 made in the end shield 29centric to the rotor shaft 2 is closed by means of a flexible, thindiaphragm 64 which is made thicker in the area of the rotor shaft 2 toform a support or block 65. When the fan wheel 4 is pressed onto therotor shaft 2, it is necessary to support the opposite end of the rotorshaft 2 so as to prevent the axial forces necessary for pressing it onfrom being transmitted to the second rotor bearing 28, the second motorhousing part 9 and the structural component parts of the rotor andpossibly destroying these structural component parts.

In the case of the embodiment example shown in FIG. 1, this support iseffected by a counter-piece reaching through the open opening 63.However, this open construction is disadvantageous in that contaminantscan enter the motor housing 8, 9. In the embodiment example shown inFIG. 8, the opening 63 is closed by the diaphragm 64. Nevertheless, acounter-piece serving to support the rotor shaft 2 when the fan wheel 4is being pressed on can act at and support the rotor shaft 2 with theintermediary of the block-like thickened portion 65 of the diaphragm 64.The flexible thin design of the diaphragm 64 prevents an axial transferof force onto the second end shield 29.

The invention is not limited to the embodiment examples shown herein andcan also realized with small commutator motors 1 of other constructionaltypes. For example, FIG. 9 shows a small commutator motor 1 in which thecommutator 18 is arranged on the side remote of the fan wheel 4. Thisimproves the accessibility of the brushes 16.

What is claimed is:
 1. Small commutator motor (1), in particular ablower motor for motor vehicles, with a rotor shaft (2) mounted in atleast a first rotor bearing (12) in a motor housing (8, 9), a commutator(18) fixedly arranged on the rotor shaft (2) so as to rotate jointlywith the latter, an armature winding (21) arranged on the rotor shaft(2) so as to be fixed with respect to rotation relative to it andelectrically connected with the commutator (18), brush guides (11) forreceiving brushes (16) held in a sliding contact on the commutator (18),and at least a first end shield (10) which fixes the first rotor bearing(12) in place, the first end shield (10) and the brush guides (11) areformed as a one-piece structural component part which is a componentpart of the motor housing (8, 9) as a first motor housing (8), and therotor shaft (2) is additionally mounted in a second rotor bearing (28)which is fixed to a second end shield (29) which is formed integral witha second motor housing part (9), the second motor housing part (9) hasan essentially radial flange (33) to which are fitted components (34) ofcontrol electronics and/or at least one protective resistor.
 2. Smallcommuter motor according to claim 1, characterized in that the firstmotor housing part (8) can be connected with the second motor housingpart 99) to form a two-piece motor housing (8, 9) in that the firstmotor housing part (8) closes the second motor housing part (9) in themanner of a lid.
 3. Small commutator motor according to claim 1,characterized in that the first motor housing part (8) and/or the secondmotor housing part (9) are/is formed as a plastic injection molded part.4. Small commutator motor according to claim 1, characterized in thatthe first rotor bearing (12) is locked to the first end shield (10)and/or the second rotor bearing (28) is locked to the second end shield(29), in each instance by means of a ring-shaped holding spring (15;31).
 5. Small commutator motor according to claim 4, characterized inthat the holding springs (15; 31) are fixed to the associated motorhousing part (8; 9) by riveting or by snapping in behind at least oneprojection (40) provided at the respective motor housing part (8; 9). 6.Small commutator motor according to claim 1, characterized in that apole ring (26) connecting at least two permanent magnet poles (24, 25)is pressed into the second motor housing part (9).
 7. Small commutatormotor according to claim 6, characterized in that spacer ribs (42)formed integral with the second motor housing part (9) are providedbetween the second motor housing part (9) and the pole ring (26). 8.Small commutator motor according to claim 6, characterized in that thepole ring (26) is fixed axially to the first motor housing part (8) by astop (43).
 9. Small commutator motor according to claim 6, characterizedin that the pole ring (26) is fixed axially by means of catch hooks (44)formed integral with the second motor housing part (9).
 10. Smallcommutator motor according to claim 6, characterized in that twoneighboring permanent magnet poles (24, 25) are fixed in the pole ring(26) and a spring element (51) presses each of the permanent magnet pole(24, 25) against a stop (50) projecting inward at the pole ring (26).11. Small commutator motor according to claim 6, characterized in thatthe pole ring (26) is composed of at least two shells (26 a, 26 b),these shells (26 a, 26 b) being separated by gaps (56) extending axiallyrelative to the rotor shaft (2).
 12. Small commutator motor according toclaim 1, characterized in that first metal connections (61) connectedwith the respective brushes (16) project radially from the first motorhousing part (8) and second metal connections (62) connected with thecomponents (34) of the control electronics and/or the protectiveresistor project axially from the flange (33) of the second motorhousing part (9) in direction of the first connections (61), so that thefirst and second connections (61, 62) can be connected with one another.13. Small commutator motor according to claim 1, characterized in thatthe small commutator motor (1) drives a fan wheel (4) and additionalblades (35) are fitted to the fan wheel (4) in the area of thecomponents (34) of the control electronics and/or the protectiveresistor for cooling them.
 14. Small commutator motor according to claim1, characterized in that the second end shield (29) has an opening (63)that closeable by a substantially thin diaphragm (64).